oldrc: fix crash on memory error

(cherry picked from commit ed9350a38676c62df562c483ecbc68d837d2cef8)
Signed-off-by: Pierre Ynard <linkfanel@yahoo.fr>

modules/control/rc.c

@@ -2054,6 +2054,8 @@ static input_item_t *parse_MRL( intf_thread_t *p_intf, char *psz_mrl )
     if( !psz_mrl ) return 0;
 
     psz_mrl = psz_orig = strdup( psz_mrl );
+    if( !psz_mrl )
+        return NULL;
     while( *psz_mrl )
     {
         SKIPSPACE( psz_mrl );